U.S. patent number 8,168,731 [Application Number 13/124,694] was granted by the patent office on 2012-05-01 for curable resin composition, cured product thereof, printed wiring board, epoxy resin, and process for producing the same.
This patent grant is currently assigned to DIC Corporation. Invention is credited to Kazuo Arita, Ichirou Ogura, Yutaka Satou.
United States Patent |
8,168,731 |
Satou , et al. |
May 1, 2012 |
Curable resin composition, cured product thereof, printed wiring
board, epoxy resin, and process for producing the same
Abstract
Provided is a curable resin composition that exhibits good heat
resistance and low thermal expansion, and that realizes good
solubility in solvents, a cured product thereof, a printed wiring
board including the composition, a novel epoxy resin that imparts
these properties, and a process for producing the same. A curable
resin composition contains, as essential components, an epoxy resin
(A) having, in its molecular structure, a glycidyloxy group and a
skeleton in which a naphthalene structure and a cyclohexadienone
structure are bonded to each other via methylene group(s); and a
curing agent (B).
Inventors: |
Satou; Yutaka (Ichihara,
JP), Arita; Kazuo (Ichihara, JP), Ogura;
Ichirou (Ichihara, JP) |
Assignee: |
DIC Corporation (Tokyo,
JP)
|
Family
ID: |
42119219 |
Appl.
No.: |
13/124,694 |
Filed: |
August 7, 2009 |
PCT
Filed: |
August 07, 2009 |
PCT No.: |
PCT/JP2009/064024 |
371(c)(1),(2),(4) Date: |
July 11, 2011 |
PCT
Pub. No.: |
WO2010/047169 |
PCT
Pub. Date: |
April 29, 2010 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20110259628 A1 |
Oct 27, 2011 |
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Foreign Application Priority Data
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Oct 22, 2008 [JP] |
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2008-271898 |
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Current U.S.
Class: |
525/481; 525/523;
525/533; 525/524; 174/255; 525/423; 428/301.1 |
Current CPC
Class: |
C08G
59/3218 (20130101); H05K 1/03 (20130101); C08G
59/08 (20130101); Y10T 428/249951 (20150401); Y10T
156/10 (20150115); H05K 1/0326 (20130101) |
Current International
Class: |
B32B
27/04 (20060101); C08L 63/00 (20060101); H05K
1/03 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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3137202 |
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Aug 1992 |
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JP |
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05-025248 |
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Feb 1993 |
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JP |
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05-032760 |
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Feb 1993 |
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JP |
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05-093036 |
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Apr 1993 |
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JP |
|
05-186547 |
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Jul 1993 |
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JP |
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2000-103941 |
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Apr 2000 |
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JP |
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2000-336248 |
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Dec 2000 |
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JP |
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2005-097352 |
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Apr 2005 |
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JP |
|
Primary Examiner: Sellers; Robert
Attorney, Agent or Firm: Edwards Wildman Palmer LLP
Claims
The invention claimed is:
1. A curable resin composition comprising, as essential components,
an epoxy resin (A) having, in its molecular structure, a
glycidyloxy group and a skeleton in which a naphthalene structure
and a cyclohexadienone structure are bonded to each other via
methylene group(s); and a curing agent (B).
2. The curable resin composition according to claim 1, wherein the
cyclohexadienone structure present in the molecular structure of
the epoxy resin (A) is a 2-naphthalenone structure.
3. The curable resin composition according to claim 2, wherein the
epoxy resin (A) contains a compound (a) having a skeleton
represented by structural formula (i) below: ##STR00020## (wherein
R.sup.1s each independently represent a hydrogen atom, a
hydrocarbon group having 1 to 4 carbon atoms, or an alkoxy group
having 1 to 2 carbon atoms.
4. The curable resin composition according to claim 3, wherein the
epoxy resin (A) has an epoxy equivalent of 150 to 300 g/eq.
5. The curable resin composition according to claim 2, wherein the
epoxy resin (A) has a molecular structure obtained by allowing a
2,7-dihydroxynaphthalene type compound to react with formaldehyde
in the presence of an alkali catalyst in an amount 0.2 to 2.0 times
the 2,7-dihydroxynaphthalene type compound on a molar basis, and
then allowing an epihalohydrin to react with the resulting reaction
product.
6. A cured product obtained by conducting a curing reaction of the
curable resin composition according to claim 1.
7. A printed wiring board obtained by impregnating a reinforcing
base material with a varnish-like resin composition prepared by
further blending an organic solvent (C) with the composition
according to claim 1, laminating a copper foil, and performing
thermocompression bonding.
8. An epoxy resin comprising, in its molecular structure, a
glycidyloxy group and a skeleton in which a naphthalene structure
and a cyclohexadienone structure are bonded to each other via
methylene group(s).
9. The epoxy resin according to claim 8, wherein the epoxy resin
has a structural formula (i) below: ##STR00021## (wherein R.sup.1s
each independently represent a hydrogen atom, a hydrocarbon group
having 1 to 4 carbon atoms, or an alkoxy group having 1 to 2 carbon
atoms.
10. An epoxy resin comprising a molecular structure obtained by
allowing a 2,7-dihydroxynaphthalene type compound to react with
formaldehyde in the presence of an alkali catalyst in an amount 0.2
to 2.0 times the 2,7-dihydroxynaphthalene type compound on a molar
basis, and then allowing an epihalohydrin to react with the
resulting reaction product.
11. A cured product obtained by conducting a curing reaction of the
curable resin composition according to claim 2.
12. A cured product obtained by conducting a curing reaction of the
curable resin composition according to claim 3.
13. A cured product obtained by conducting a curing reaction of the
curable resin composition according to claim 4.
14. A cured product obtained by conducting a curing reaction of the
curable resin composition according to claim 5.
15. A printed wiring board obtained by impregnating a reinforcing
base material with a varnish-like resin composition prepared by
further blending an organic solvent (C) with the composition
according to claim 2, laminating a copper foil, and performing
thermocompression bonding.
16. A printed wiring board obtained by impregnating a reinforcing
base material with a varnish-like resin composition prepared by
further blending an organic solvent (C) with the composition
according to claim 3, laminating a copper foil, and performing
thermocompression bonding.
17. A printed wiring board obtained by impregnating a reinforcing
base material with a varnish-like resin composition prepared by
further blending an organic solvent (C) with the composition
according to claim 4, laminating a copper foil, and performing
thermocompression bonding.
18. A printed wiring board obtained by impregnating a reinforcing
base material with a varnish-like resin composition prepared by
further blending an organic solvent (C) with the composition
according to claim 5, laminating a copper foil, and performing
thermocompression bonding.
Description
TECHNICAL FIELD
The present invention relates to a curable resin composition whose
cured product has good heat resistance and low thermal expansion
and which can be suitably used for applications to a printed wiring
board, a semiconductor sealing material, a coating material, cast
molding, and the like, a cured product thereof, a novel epoxy
resin, a process for producing the same, and a printed wiring board
that is good in terms of heat resistance and low thermal
expansion.
BACKGROUND ART
Epoxy resins are used as an adhesive, a molding material, a coating
material, a photoresist material, a color developer, etc. In
addition, epoxy resins are widely used in the electric/electronic
fields such as a semiconductor sealing material and an insulating
material for a printed wiring board from the standpoint of good
heat resistance, moisture resistance, and the like of the resulting
cured products.
Among these various applications, in the field of printed wiring
boards, with a trend of a reduction in the size and an increase in
the performance of electronic devices, a trend of realizing a high
density by reducing the wiring pitch of semiconductor devices has
been significant. As a semiconductor packaging method for meeting
this trend, a flip-chip connection method in which a semiconductor
device is bonded to a substrate with solder balls is widely used.
This flip-chip connection method is a semiconductor packaging
method using a so-called reflow process in which solder balls are
arranged between a wiring board and a semiconductor, and fusion
bonding is performed by heating the whole components. Accordingly,
during the solder reflow, the wiring board itself is exposed to a
high-heat environment, and a large stress is generated, by thermal
contraction of the wiring board, in the solder balls connecting the
wiring board to the semiconductor, which may result in connection
failure of wiring. Therefore, a material having a low coefficient
of thermal expansion has been desired for an insulating material
used as a printed wiring board.
In addition, recently, lead-free high-melting point solder has been
widely used because of, for example, regulations associated with
environmental issues. This lead-free solder is used at a
temperature about 20.degree. C. to 40.degree. C. higher than the
temperature used for existing eutectic solder. Thus, a heat
resistance higher than ever before is required for curable resin
compositions.
As described above, high heat resistance and low thermal expansion
have been desired for insulating materials for printed wiring
boards. As an epoxy resin material that can meet such requirements,
for example, a tetrafunctional naphthalene epoxy resin represented
by the structural formula below is known (refer to PTL 1
below).
##STR00001##
The above tetrafunctional naphthalene epoxy resin has a
crosslinking density higher than that of general phenol
novolac-type epoxy resins, and thus good low thermal linear
expansion and heat resistance are exhibited in cured products of
the epoxy resin. However, recently, higher performance has been
required, and it has been necessary to achieve a further
improvement. Furthermore, since the tetrafunctional naphthalene
epoxy resin has low solubility in solvents that are generally used
in the production of printed wiring boards, characteristics of
resulting cured products are not sufficiently exhibited.
CITATION LIST
Patent Literature
PTL 1: Japanese Patent No. 3137202
SUMMARY OF INVENTION
Technical Problem
Accordingly, an object to be achieved by the present invention is
to provide a curable resin composition that exhibits good heat
resistance and low thermal expansion and that realizes good
solubility in solvents, a cured product thereof, a printed wiring
board that is good in terms of heat resistance and low thermal
expansion, an epoxy resin that imparts these properties, and a
process for producing the same.
Solution to Problem
In order to achieve the above object, the inventors of the present
invention conducted intensive studies. As a result, it was found
that an epoxy resin having a carbonyl group, the epoxy resin being
obtained by allowing a 2,7-dihydroxynaphthalene type compound to
react with formaldehyde under a specific condition, and then
allowing the resulting reaction product to react with
epichlorohydrin, exhibits good heat resistance and low thermal
expansion, and has good solubility in solvents. This finding
resulted in the completion of the present invention.
Specifically, the present invention relates to a curable resin
composition containing, as essential components, an epoxy resin (A)
having, in its molecular structure, a glycidyloxy group and a
skeleton in which a naphthalene structure and a cyclohexadienone
structure are bonded to each other via methylene group(s); and a
curing agent (B).
The present invention further relates to a cured product obtained
by conducting a curing reaction of the above curable resin
composition.
The present invention further relates to a printed wiring board
obtained by impregnating a glass woven cloth with a resin
composition containing, as essential components, an epoxy resin (A)
having, in its molecular structure, a glycidyloxy group and a
skeleton in which a naphthalene structure and a cyclohexadienone
structure are bonded to each other via methylene group(s), a curing
agent (B), and an organic solvent (C), laminating a copper foil,
and performing thermocompression bonding.
The present invention further relates to an epoxy resin having, in
its molecular structure, a glycidyloxy group and a skeleton in
which a naphthalene structure and a cyclohexadienone structure are
bonded to each other via methylene group(s).
The present invention further relates to an epoxy resin having a
molecular structure obtained by allowing a 2,7-dihydroxynaphthalene
type compound to react with formaldehyde in the presence of an
alkali catalyst in an amount 0.2 to 2.0 times the
2,7-dihydroxynaphthalene type compound on a molar basis, and then
allowing an epihalohydrin to react with the resulting reaction
product.
The present invention further relates to a process for producing an
epoxy resin including allowing a 2,7-dihydroxynaphthalene type
compound to react with formaldehyde in the presence of an alkali
catalyst in an amount 0.2 to 2.0 times the 2,7-dihydroxynaphthalene
type compound on a molar basis, and then allowing an epihalohydrin
to react with the resulting reaction product.
Advantageous Effects of Invention
According to the present invention, it is possible to provide a
curable resin composition that exhibits good heat resistance and
low thermal expansion, and that realizes good solubility in
solvents, a cured product thereof, a printed wiring board that is
good in terms of heat resistance and low thermal expansion, an
epoxy resin that imparts these properties, and a process for
producing the same.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a gel permeation chromatography (GPC) chart of a phenolic
compound obtained in Example 1.
FIG. 2 is a .sup.13C-NMR spectrum of the phenolic compound obtained
in Example 1.
FIG. 3 is a mass spectrum of the phenolic compound obtained in
Example 1.
FIG. 4 is a GPC chart of an epoxy resin obtained in Example 1.
FIG. 5 is a .sup.13C-NMR spectrum of the epoxy resin obtained in
Example 1.
FIG. 6 is a mass spectrum of the epoxy resin obtained in Example
1.
FIG. 7 is a GPC chart of an epoxy resin obtained in Example 2.
FIG. 8 is a .sup.13C-NMR spectrum of the epoxy resin obtained in
Example 2.
FIG. 9 is a mass spectrum of the epoxy resin obtained in Example
2.
DESCRIPTION OF EMBODIMENTS
The present invention will now be described in detail.
An epoxy resin (A) used in the present invention is characterized
in that the epoxy resin (A) has, in its molecular structure, a
glycidyloxy group and a skeleton in which a naphthalene structure
and a cyclohexadienone structure are bonded to each other via
methylene group(s). That is, since the epoxy resin (A) has, in its
molecule, a skeleton in which a naphthalene structure and a
cyclohexadienone structure are bonded to each other via methylene
group(s), good solubility in solvents can be exhibited on the basis
of the chemical structural asymmetry of the epoxy resin (A).
Furthermore, in a curing reaction between an epoxy group and a
curing agent, the cyclohexadienone structure is involved in the
curing reaction, whereby a strong cured product is obtained and
heat resistance and low thermal expansion in the cured product are
improved.
Herein, specifically, examples of the cyclohexadienone structure
include 2,4-cyclohexadienone structures represented by structural
formulae k1 and k2 below:
##STR00002## and a 2,5-cyclohexadienone structure represented by
structural formula k3 below:
##STR00003##
Among these structures, the 2,4-cyclohexadienone structures
represented by structural formulae k1 and k2 above are preferable
from the standpoint of significantly good heat resistance and low
thermal expansion, and in particular, a 2-naphthalenone structure
represented by structural formula k1 above is preferable.
The epoxy resin (A) can be produced by a process in which a
2,7-dihydroxynaphthalene type compound is allowed to react with
formaldehyde in the presence of an alkali catalyst, and the
resulting reaction product is then allowed to react with an
epihalohydrin (process 1) or a process in which a
2,7-dihydroxynaphthalene type compound, formaldehyde, and a phenol
are allowed to react with each other in the presence of an alkali
catalyst, and the resulting reaction product is then allowed to
react with an epihalohydrin (process 2), and can include epoxy
resins having various molecular structures. Specifically, the epoxy
resin (A) preferably contains a compound (a) having, as a basic
skeleton, a structure in which a naphthalene structure and a
cyclohexadienone structure represented by structural formula k1 or
k2 above are bonded to each other via methylene group(s) and having
a glycidyloxy group as a substituent on the aromatic nucleus of the
basic skeleton.
Specifically, examples of the compound (a) include compounds
represented by structural formulae (i) to (iii) below:
##STR00004##
In structural formulae (i) to (iii) above, R.sup.1s each
independently represent a hydrogen atom, a hydrocarbon group having
1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms.
Specifically, examples of the compounds represented by structural
formula (i) above include compounds represented by i-1 to i-8
below.
##STR00005## ##STR00006##
Examples of the compounds represented by structural formula (ii)
above include compounds represented by ii-1 to ii-8 below.
##STR00007## ##STR00008##
Examples of the compounds represented by structural formula (iii)
above include compounds represented by iii-1 to iii-8 below.
##STR00009## ##STR00010##
Among these compounds, the compound represented by structural
formula (i) below:
##STR00011## (wherein R.sup.1s each independently represent a
hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, or
an alkoxy group having 1 to 4 carbon atoms) is particularly
preferable from the standpoint of significantly good heat
resistance and low thermal expansion. As described above, the
compound represented by structural formula (i) above has a
cyclohexadienone structure in its molecule. Accordingly, the
compound is asymmetric in terms of the chemical structure and can
exhibit good solubility in solvents. In addition, since the
cyclohexadienone structure itself contributes to a curing reaction
with a curing agent (B), the compound represented by structural
formula (i) above can exhibit good heat resistance and low thermal
expansion though the compound is a trifunctional epoxy resin.
In the present invention, among these, from the standpoint of
particularly high heat resistance, the compound (a) preferably has
a structure represented by structural formula (i-.alpha.)
below:
##STR00012## in which R.sub.1s in structural formula (i) are each a
hydrogen atom.
When the epoxy resin (A) described in detail above is produced by
the above process 1 or process 2, in general, in addition to the
compound (a), a compound (b) represented by structural formula (iv)
below:
##STR00013## an epoxy resin oligomer (c) in which a structural site
represented by a partial structural formula (v) below:
##STR00014## is further bonded to the aromatic nucleus in
structural formula (i), structural formula (ii), or structural
formula (iii) above; and furthermore, an oligomer (d) that is
produced when an epihalohydrin is allowed to react in the process 1
or the process 2 are also produced. Accordingly, the epoxy resin
(A) of the present invention may be used as a mixture of these.
In this case, the epoxy resin (A) preferably contains the compound
(a) in an amount of 5.0% to 20.0% by mass. Specifically, the epoxy
resin (A) preferably contains the compound (a) in an amount of 5.0%
to 20.0% by mass, the compound (b) in an amount of 15.0% to 50.0%
by mass, and an oligomer component typified by the oligomer (c) or
the oligomer (d) in an amount of 30% to 80% by mass from the
standpoint of good solubility in solvents.
In addition, from the standpoint that good heat resistance and low
thermal expansion can be achieved, the epoxy equivalent in the
epoxy resin (A) is preferably in the range of 150 to 300 g/eq, and
particularly preferably in the range of 155 to 250 g/eq.
As described above, the epoxy resin (A) can be produced by the
process 1 or the process 2, but the present invention is
characterized in that the amount of alkali catalyst is larger than
that in the production of existing compounds. Specifically, the
skeleton in which a naphthalene structure and a cyclohexadienone
structure are bonded to each other via methylene group(s) can be
produced in the molecular structure by using an alkali catalyst, on
a molar basis, 0.2 to 2.0 times the number of moles of a
2,7-dihydroxynaphthalene type compound or the total number of moles
of a 2,7-dihydroxynaphthalene type compound and a phenol. In
contrast, a compound represented by structural formula (2)
below:
##STR00015## which is a known compound, can be produced by allowing
2,7-dihydroxynaphthalene type compound to react with formaldehyde
using an alkali catalyst in an amount 0.01 to 0.1 times the amount
of 2,7-dihydroxynaphthalene type compound on a molar basis.
However, in such an amount of the catalyst, during the production
process, the compound represented by structural formula (2) is
selectively produced and precipitated, and the reaction is then
terminated. Therefore, unlike the present invention, a
cyclohexadienone structure is not produced.
Herein, examples of the 2,7-dihydroxynaphthalene type compound used
in the process 1 or the process 2 include 2,7-dihydroxynaphthalene,
methyl-2,7-dihydroxynaphthalene, ethyl-2,7-dihydroxynaphthalene,
tert-butyl-2,7-dihydroxynaphthalene,
methoxy-2,7-dihydroxynaphthalene, and
ethoxy-2,7-dihydroxynaphthalene.
The formaldehyde used in the process 1 or the process 2 may be a
formalin solution, which is in the state of an aqueous solution, or
paraformaldehyde, which is in the state of a solid.
Examples of the phenol used in the process 2 include phenol,
o-cresol, p-cresol, and 2,4-xylenol.
Examples of the alkali catalyst used in the process 1 or the
process 2 include alkali metal hydroxides such as sodium hydroxide
and potassium hydroxide; and inorganic alkalis such as metallic
sodium, metallic lithium, sodium hydride, sodium carbonate, and
potassium carbonate.
As described above, in the present invention, among the compounds
(a), the compound represented by structural formula (i) above is
preferable. Accordingly, of the above-described processes, the
production process of the process 1 is preferable. The process 1
will now be described in detail.
Specifically, examples of the process 1 include a process in which
a 2,7-dihydroxynaphthalene type compound and formaldehyde are
charged substantially at the same time, and a reaction is conducted
by stirring under heating in the presence of an appropriate
catalyst, and a process in which a reaction is conducted by
continuously or intermittently adding formaldehyde to a reaction
system of a mixed liquid containing a 2,7-dihydroxynaphthalene type
compound and an appropriate catalyst. Note that, herein, the phrase
"substantially at the same time" means that all the raw materials
are charged until the reaction is accelerated by heating.
Examples of the alkali catalyst used here include alkali metal
hydroxides such as sodium hydroxide and potassium hydroxide; and
inorganic alkalis such as metallic sodium, metallic lithium, sodium
hydride, sodium carbonate, and potassium carbonate. As described
above, the amount of use thereof is preferably in the range of 0.2
to 2.0 times the number of moles of the 2,7-dihydroxynaphthalene
type compound on a molar basis.
The reaction charging ratio of formaldehyde to the
2,7-dihydroxynaphthalene type compound is not particularly limited.
However, the amount of formaldehyde is preferably 0.6 to 2.0, in
particular, from the standpoint of a good balance between heat
resistance and the viscosity of the epoxy resin, 0.6 to 1.5 times
the amount of 2,7-dihydroxynaphthalene type compound on a molar
basis.
In conducting this reaction, an organic solvent may be used as
required. Examples of the organic solvent that can be used include,
but are not limited to, methyl cellosolve, isopropyl alcohol, ethyl
cellosolve, toluene, xylene, and methyl isobutyl ketone. The amount
of organic solvent used is usually in the range of 0.1 to 5 times,
particularly preferably, in the range of 0.3 to 2.5 times the total
mass of the charging raw materials from the standpoint that the
structure represented by structural formula (i) is efficiently
obtained. The reaction temperature is preferably in the range of
20.degree. C. to 150.degree. C., and in particular, more preferably
in the range of 60.degree. C. to 100.degree. C. The reaction time
is not particularly limited, but is usually in the range of 1 to 10
hours.
After the completion of the reaction, a neutralization process or a
water washing process is conducted until the pH of the reaction
mixture becomes in the range of 4 to 7. The neutralization process
or the water washing process can be conducted in accordance with
conventional process. For example, when an alkali catalyst is used,
an acidic substance such as acetic acid, phosphoric acid, or sodium
phosphate can be used as a neutralizing agent. After the
neutralization process or the water washing process is conducted,
the organic solvent is distilled off by heating under reduced
pressure to concentrate the resulting product. Thus, a carbonyl
group-containing phenolic compound can be obtained. Furthermore,
from the standpoint that inorganic salts and foreign matters can be
removed by purification, a microfiltration step is more preferably
introduced to the process operations performed after the completion
of the reaction.
Next, the resulting phenolic compound is allowed to react with an
epihalohydrin, thereby obtaining a target epoxy resin (A).
Specifically, an example of the process is as follows: The phenolic
compound is allowed to react with an epihalohydrin by adding the
epihalohydrin in an amount 2 to 10 times (on a molar basis) the
number of moles of the phenolic hydroxyl group in the phenolic
compound, and further adding a basic catalyst either at one time or
gradually in an amount 0.9 to 2.0 times (on a molar basis) the
number of moles of the phenolic hydroxyl group at a temperature in
the range of 20.degree. C. to 120.degree. C. for 0.5 to 10 hours.
This basic catalyst may be used either in the form of a solid or in
the form of an aqueous solution thereof. When an aqueous solution
is used, a process may be employed in which the aqueous solution is
continuously added, water and the epihalohydrin are continuously
distilled from the reaction mixture under reduced pressure or
normal pressure, and a separation of liquid is further conducted so
that water is removed and the epihalohydrin is continuously
returned to the reaction mixture.
When industrial production is performed, in a first batch of the
production of the epoxy resin, all of the epihalohydrin used in
charging is virgin epihalohydrin. However, in subsequent batches,
the epihalohydrin recovered from a crude reaction product and
virgin epihalohydrin that compensates for the amount that has
disappeared by being consumed by the reaction are preferably used
in combination. In this case, examples of the epihalohydrin used
include, but are not particularly limited to, epichlorohydrin,
epibromohydrin, and .beta.-methylepichlorohydrin. Among these,
epichlorohydrin is preferable from the standpoint of the ease of
industrial availability.
Specifically, examples of the basic catalyst include alkaline earth
metal hydroxides, alkali metal carbonates, and alkali metal
hydroxides. In particular, from the standpoint of high catalytic
activity of an epoxy resin synthesis reaction, alkali metal
hydroxides are preferable. Examples thereof include sodium
hydroxide and potassium hydroxide. In using the basic catalyst,
these basic catalysts may be used either in the form of an aqueous
solution with a concentration of about 10% to 55% by mass or in the
form of a solid. Furthermore, the reaction rate in the synthesis of
the epoxy resin can be increased by using an organic solvent in
combination. Examples of the organic solvent include, but are not
particularly limited to, ketones such as acetone and methyl ethyl
ketone; alcohols such as methanol, ethanol, 1-propyl alcohol,
isopropyl alcohol, 1-butanol, secondary butanol, and tertiary
butanol; cellosolves such as methyl cellosolve and ethyl
cellosolve; ethers such as tetrahydrofuran, 1,4-dioxane,
1,3-dioxane, and diethoxyethane; and aprotic polar solvents such as
acetonitrile, dimethyl sulfoxide, and dimethylformamide. These
organic solvents may be used alone or appropriately in combination
of two or more solvents in order to adjust the polarity.
After the above-described reaction product of the epoxidation
reaction is washed with water, distillation is performed by heating
under reduced pressure so that unreacted epihalohydrin and the
organic solvent used in combination are distilled off. In addition,
in order to produce an epoxy resin that contains a smaller amount
of hydrolyzable halogen, the resulting epoxy resin may be again
dissolved in an organic solvent such as toluene, methyl isobutyl
ketone, or methyl ethyl ketone, and an aqueous solution of an
alkali metal hydroxide such as sodium hydroxide or potassium
hydroxide may be added to the resulting solution to further conduct
a reaction. In this case, in order to improve the reaction rate,
the reaction may be conducted in the presence of a phase-transfer
catalyst such as a quaternary ammonium salt or a crown ether. When
the phase-transfer catalyst is used, the amount used is preferably
0.1 to 3.0 parts by mass relative to 100 parts by mass of the epoxy
resin used. After the completion of the reaction, the resulting
salt is removed by, for example, filtering and washing with water,
and the solvent such as toluene or methyl isobutyl ketone is
further distilled off by heating under reduced pressure. Thus, the
epoxy resin (A) containing the target compound (a) can be
obtained.
In the curable resin composition of the present invention, the
epoxy resin (A) may be used alone or other epoxy resins may be used
so long as the advantages of the present invention are not
impaired. Specifically, the other epoxy resins can be used in
combination so that the amount of the epoxy resin (A) is 30% by
mass or more, preferably 40% by mass or more of the total mass of
the epoxy resin components.
Various epoxy resins can be used as the other epoxy resins that can
be used in combination with the epoxy resin (A). Examples thereof
include bisphenol A-type epoxy resins, bisphenol F-type epoxy
resins, biphenyl-type epoxy resins, tetramethylbiphenyl-type epoxy
resins, phenol novolac-type epoxy resins, cresol novolac-type epoxy
resins, bisphenol A novolac-type epoxy resins,
triphenylmethane-type epoxy resins, tetraphenylethane-type epoxy
resins, dicyclopentadiene-phenol addition reaction-type epoxy
resins, phenol aralkyl-type epoxy resins, naphthol novolac-type
epoxy resins, naphthol aralkyl-type epoxy resin, naphthol-phenol
co-condensed novolac-type epoxy resins, naphthol-cresol
co-condensed novolac-type epoxy resins, aromatic
hydrocarbon-formaldehyde resin-modified phenolic resin-type epoxy
resins, and biphenyl novolac-type epoxy resins. Among these, phenol
aralkyl-type epoxy resins; biphenyl novolac-type epoxy resins;
naphthol novolac-type epoxy resins, naphthol aralkyl-type epoxy
resin, naphthol-phenol co-condensed novolac-type epoxy resins, and
naphthol-cresol co-condensed novolac-type epoxy resins, all of
which have a naphthalene skeleton; crystalline biphenyl-type epoxy
resins; tetramethylbiphenyl-type epoxy resins; xanthene-type epoxy
resins; and alkoxy group-containing aromatic ring-modified
novolac-type epoxy resins (compounds in which a glycidyl
group-containing aromatic ring and an alkoxy group-containing
aromatic ring are connected by formaldehyde) are particularly
preferable from the standpoint of obtaining a cured product having
good heat resistance.
Examples of the curing agent (B) used in the curable resin
composition of the present invention include amine compounds, amide
compounds, acid anhydride compounds, and phenolic compounds.
Specifically, examples of the amine compounds include
diaminodiphenylmethane, diethylenetriamine, triethylenetetramine,
diaminodiphenyl sulfone, isophoronediamine, imidazoles,
BF.sub.3-amine complexes, and guanidine derivatives. Specific
examples of the amide compounds include dicyandiamide, and
polyamide resins synthesized from a dimer of linolenic acid and
ethylenediamine. Specific examples of the acid anhydride compounds
include phthalic anhydride, trimellitic anhydride, pyromellitic
anhydride, maleic anhydride, tetrahydrophthalic anhydride,
methyltetrahydrophthalic anhydride, methylnadic anhydride,
hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride.
Specific examples of the phenolic compounds include phenol novolac
resins, cresol novolac resins, aromatic hydrocarbon-formaldehyde
resin-modified phenolic resins, dicyclopentadiene-phenol addition
type resins, phenol aralkyl resins (xylok resins), naphthol aralkyl
resins, trimethylolmethane resins, tetraphenylolethane resins,
naphthol novolac resins, naphthol-phenol co-condensed novolac
resins, naphthol-cresol co-condensed novolac resins, and polyvalent
phenolic compounds such as biphenyl-modified phenolic resins
(polyvalent phenolic compounds in which phenolic nuclei are
connected by a bismethylene group), biphenyl-modified naphthol
resins (polyvalent naphthol compounds in which phenolic nuclei are
connected by a bismethylene group), aminotriazine-modified phenolic
resins (polyvalent phenolic compounds in which phenolic nuclei are
connected by melamine, benzoguanamine, or the like), and alkoxy
group-containing aromatic ring-modified novolac resins (polyvalent
phenolic compounds in which a phenolic nucleus and an alkoxy
group-containing aromatic ring are connected by formaldehyde).
Among these, in particular, compounds having a large number of
aromatic skeletons in the molecular structure are preferable from
the standpoint of low thermal expansion. Specifically, phenol
novolac resins, cresol novolac resins, aromatic
hydrocarbon-formaldehyde resin-modified phenolic resins, phenol
aralkyl resins, naphthol aralkyl resins, naphthol novolac resins,
naphthol-phenol co-condensed novolac resins, naphthol-cresol
co-condensed novolac resins, biphenyl-modified phenolic resins,
biphenyl-modified naphthol resins, aminotriazine-modified phenolic
resins, and alkoxy group-containing aromatic ring-modified novolac
resins (polyvalent phenolic compounds in which a phenolic nucleus
and an alkoxy group-containing aromatic ring are connected by
formaldehyde) are preferable because these compounds are good in
terms of low thermal expansion.
The blending ratio of the epoxy resin (A) and the curing agent (B)
in the curable resin composition of the present invention is not
particularly limited. However, from the standpoint that
characteristics of the resulting cured product are good, the amount
of an active group in the curing agent (B) is preferably 0.7 to 1.5
equivalents relative to the total 1 equivalent of the epoxy group
of the epoxy resin (A).
In addition, a curing accelerator may be appropriately used in
combination with the curable resin composition of the present
invention, as required. Various types of compounds can be used as
the curing accelerator. Examples of the curing accelerator include
phosphorus compounds, tertiary amines, imidazoles, organic acid
metal salts, Lewis acids, and amine complex salts. In particular,
when the curable resin composition is used in the application of
semiconductor-sealing materials, among the phosphorous compounds,
triphenylphosphine is preferable, and among the tertiary amines,
1,8-diazabicyclo-[5.4.0]-undecene (DBU) is preferable from the
standpoint of good curability, heat resistance, electrical
properties, moisture resistance reliability etc.
As described above, the curable resin composition of the present
invention described in detail above has a feature that the curable
resin composition exhibits good solubility in solvents.
Accordingly, the curable resin composition preferably contains an
organic solvent (C) in addition to the components described above.
Examples of the organic solvent (C) that can be used here include
methyl ethyl ketone, acetone, dimethylformamide, methyl isobutyl
ketone, methoxy propanol, cyclohexanone, methyl cellosolve, ethyl
diglycol acetate, and propylene glycol monomethyl ether acetate.
The selection and a proper amount of the organic solvent used can
be appropriately selected depending on the applications. For
example, in the application of printed wiring boards, polar
solvents having a boiling point of 160.degree. C. or lower, e.g.,
methyl ethyl ketone, acetone, and dimethylformamide are preferable,
and these solvents are preferably used so that the proportion of
the non-volatile matter is 40% to 80% by mass. On the other hand,
in the application of adhesive films for build-up, as the organic
solvent (C), for example, ketones such as acetone, methyl ethyl
ketone, and cyclohexanone; acetic acid esters such as ethyl
acetate, butyl acetate, cellosolve acetate, propylene glycol
monomethyl ether acetate, and carbitol acetate; cellosolves;
carbitols such as butyl carbitol; aromatic hydrocarbons such as
toluene and xylene; dimethylformamide; dimethylacetamide; and
N-methylpyrrolidone are preferably used. These solvents are
preferably used so that the proportion of the non-volatile matter
is 30% to 60% by mass.
Furthermore, in order to exhibit flame retardancy, for example, in
the field of the printed wiring board, the curable resin
composition may contain a non-halogen flame retardant that
substantially contains no halogen atoms within the range that does
not degrade reliability.
Examples of the non-halogen flame retardant include
phosphorus-based flame retardants, nitrogen-based flame retardants,
silicone-based flame retardants, inorganic flame retardants, and
organic metal salt-based flame retardants. The use of these flame
retardants is not limited. These flame retardants may be used alone
or a plurality of similar types of flame retardants may be used.
Alternatively, different types of flame retardants may be used in
combination.
As the phosphorus-based flame retardants, both inorganic compounds
and organic compounds can be used. Examples of the inorganic
compounds include red phosphorus; ammonium phosphates such as
monoammonium phosphate, diammonium phosphate, triammonium
phosphate, and ammonium polyphosphate; and inorganic
nitrogen-containing phosphorus compounds such as phosphoric acid
amide.
The red phosphorus is preferably subjected to a surface treatment
in order to prevent hydrolysis or the like. Examples of the process
of the surface treatment include (i) a process of coating with an
inorganic compound such as magnesium hydroxide, aluminum hydroxide,
zinc hydroxide, titanium hydroxide, bismuth oxide, bismuth
hydroxide, bismuth nitrate, or a mixture thereof, (ii) a process of
coating with a mixture of an inorganic compound such as magnesium
hydroxide, aluminum hydroxide, zinc hydroxide, or titanium
hydroxide and a thermosetting resin such as a phenolic resin, and
(iii) a process of coating with a film composed of an inorganic
compound such as magnesium hydroxide, aluminum hydroxide, zinc
hydroxide, or titanium hydroxide and further coating the inorganic
compound film with a film composed of a thermosetting resin such as
a phenolic resin.
Examples of the organic phosphorus-based compound include
general-purpose organic phosphorus-based compounds such as
phosphate ester compounds, phosphonic acid compounds, phosphinic
acid compounds, phosphine oxide compounds, phosphorane compounds,
and organic nitrogen-containing phosphorus compounds. Besides these
compounds, examples thereof further include cyclic organic
phosphorus compounds such as
9,10-dihydro-9-oxa-10-phosphaphenanthrene=10-oxide,
10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene=10-oxide,
and
10-(2,7-dihydroxynaphthyl)-10H-9-oxa-10-phosphaphenanthrene=10-oxide;
and derivatives obtained by allowing any of these compounds to
react with a compound such as an epoxy resin or a phenolic
resin.
The amount of the phosphorus-based flame retardant is appropriately
selected in accordance with the type of phosphorus-based flame
retardant, other components of the curable resin composition, and
the degree of desired flame retardancy. For example, when red
phosphorus is used as the non-halogen flame retardant in 100 parts
by mass of a curable resin composition containing all components,
such as an epoxy resin, a curing agent, a non-halogen flame
retardant, and other fillers and additives, red phosphorus is
preferably incorporated in an amount in the range of 0.1 to 2.0
parts by mass. When an organic phosphorous compound is used,
similarly, the organic phosphorous compound is incorporated in an
amount preferably in the range of 0.1 to 10.0 parts by mass, and
particularly preferably in the range of 0.5 to 6.0 parts by
mass.
When the phosphorous-based flame retardant is used, the
phosphorous-based flame retardant may be used in combination with,
for example, hydrotalcite, magnesium hydroxide, a boron compounds,
zirconium oxide, black dyes, calcium carbonate, zeolite, zinc
molybdate, or activated carbon.
Examples of the nitrogen-based flame retardant include triazine
compounds, cyanuric acid compounds, isocyanuric acid compounds, and
phenothiazine. Triazine compounds, cyanuric acid compounds, and
isocyanuric acid compounds are preferable.
Examples of the triazine compound include melamine, acetoguanamine,
benzoguanamine, melon, melam, succinoguanamine, ethylenedimelamine,
melamine polyphosphate, and triguanamine. Besides these compounds,
examples thereof further include (i) aminotriazine sulfate
compounds such as guanylmelamine sulfate, melem sulfate, and melam
sulfate; (ii) cocondensates of a phenol such as phenol, cresol,
xylenol, butylphenol, or nonylphenol, a melamine such as melamine,
benzoguanamine, acetoguanamine, or formguanamine, and formaldehyde;
(iii) mixtures of the cocondensate (ii) mentioned above and a
phenolic resin such as a phenol-formaldehyde condensate; and (iv)
those obtained by modifying the cocondensate (ii) or the mixture
(iii) with, for example, tung oil or isomerized linseed oil.
Specific examples of the cyanuric acid compound include cyanuric
acid and melamine cyanurate.
The amount of the nitrogen-based flame retardant is appropriately
selected in accordance with the type of nitrogen-based flame
retardant, other components of the curable resin composition, and
the degree of desired flame retardancy. For example, the
nitrogen-based flame retardant is preferably incorporated within
the range of 0.05 to 10 parts by mass, and particularly preferably
0.1 to 5 parts by mass relative to 100 parts by mass of a curable
resin composition containing all components, such as an epoxy
resin, a curing agent, a non-halogen flame retardant, and other
fillers and additives.
When the nitrogen-based flame retardant is used, for example, a
metal hydroxide or a molybdenum compound may be used in
combination.
The silicone-based flame retardants are not particularly limited so
long as the flame retardant is an organic compound having a silicon
atom, and examples thereof include silicone oil, silicone rubber,
and silicone resins.
The amount of the silicone-based flame retardant is appropriately
selected in accordance with the type of silicone-based flame
retardant, other components of the curable resin composition, and
the degree of desired flame retardancy. For example, the
silicone-based flame retardant is preferably incorporated within
the range of 0.05 to 20 parts by mass relative to 100 parts by mass
of a curable resin composition containing all components, such as
an epoxy resin, a curing agent, a non-halogen flame retardant, and
other fillers and additives. When the silicone-based flame
retardant is used, for example, a molybdenum compound or alumina
may be used in combination.
Examples of the inorganic flame retardant include metal hydroxides,
metal oxides, metal carbonate compounds, metal powders, boron
compounds, and low-melting-point glass.
Specific examples of the metal hydroxide include aluminum
hydroxide, magnesium hydroxide, dolomite, hydrotalcite, calcium
hydroxide, barium hydroxide, and zirconium hydroxide.
Specific examples of the metal oxide include zinc molybdate,
molybdenum trioxide, zinc stannate, tin oxide, aluminum oxide, iron
oxide, titanium oxide, manganese oxide, zirconium oxide, zinc
oxide, molybdenum oxide, cobalt oxide, bismuth oxide, chromium
oxide, nickel oxide, copper oxide, and tungsten oxide.
Specific examples of the metal carbonate compound include zinc
carbonate, magnesium carbonate, calcium carbonate, barium
carbonate, basic magnesium carbonate, aluminum carbonate, iron
carbonate, cobalt carbonate, and titanium carbonate.
Specific examples of the metal powder include powders of aluminum,
iron, titanium, manganese, zinc, molybdenum, cobalt, bismuth,
chromium, nickel, copper, tungsten, and tin.
Specific examples of the boron compound include zinc borate, zinc
metaborate, barium metaborate, boric acid, and borax.
Specific examples of the low-melting-point glass include Seaplea
(Bokusui Brown Co., Ltd.), hydrated glass SiO.sub.2--MgO--H.sub.2O,
PbO--B.sub.2O.sub.3-based, ZnO--P.sub.2O.sub.5--MgO-based,
P.sub.2O.sub.5--B.sub.2O.sub.3--PbO--MgO-based, P--Sn--O--F-based,
PbO--V.sub.2O.sub.5--TeO.sub.2-based,
Al.sub.2O.sub.3--H.sub.2O-based, and lead borosilicate-based glassy
compounds.
The amount of the inorganic flame retardant is appropriately
selected in accordance with the type of inorganic flame retardant,
other components of the curable resin composition, and the degree
of desired flame retardancy. For example, the inorganic flame
retardant is preferably incorporated within the range of 0.05 to 20
parts by mass, and particularly preferably from 0.5 to 15 parts by
mass relative to 100 parts by mass of a curable resin composition
containing all components, such as an epoxy resin, a curing agent,
a non-halogen flame retardant, and other fillers and additives.
Examples of the organic metal salt-based flame retardant include
ferrocene, acetylacetonate metal complexes, organometallic carbonyl
compounds, organic cobalt salt compounds, organic sulfonic acid
metal salts, and compounds obtained by ionic bonding or coordinate
bonding of a metal atom and an aromatic compound or a heterocyclic
compound.
The amount of the organic metal salt-based flame retardant is
appropriately selected in accordance with the type of organic metal
salt-based flame retardant, other components of the curable resin
composition, and the degree of desired flame retardancy. For
example, the organic metal salt-based flame retardant is preferably
incorporated within the range of 0.005 to 10 parts by mass relative
to 100 parts by mass of a curable resin composition containing all
components, such as an epoxy resin, a curing agent, a non-halogen
flame retardant, and other fillers and additives.
The curable resin composition of the present invention may contain
inorganic fillers, if necessary. Examples of the inorganic filler
include fused silica, crystalline silica, alumina, silicon nitride,
and aluminum hydroxide. When the amount of the inorganic filler is
particularly large, fused silica is preferably used. The fused
silica can be used in a crushed or spherical form, but it is
preferable to mainly use spherical fused silica in order to
increase the amount of fused silica blended and to suppress an
increase in the melt viscosity of the resulting molding material.
In order to further increase the amount of spherical silica
blended, it is preferable to appropriately adjust particle size
distribution of the spherical silica. In consideration of flame
retardancy, the filling ratio of the filler is preferably high and
is particularly preferably 20% by mass or more of the total amount
of the curable resin composition. When the curable resin
composition is used in the application of an electrically
conductive paste or the like, an electrically conductive filler
such as a silver powder or a copper powder can be used.
Various compounding agents such as a silane coupling agent, a mold
release agent, a pigment, and an emulsifier may be optionally added
to the curable resin composition of the present invention.
The curable resin composition of the present invention is obtained
by uniformly mixing the above-described components. A process of
obtaining a cured product of the present invention from the curable
resin composition described in detail above may be in accordance
with a commonly used curing process of a curable resin composition.
The heating temperature condition can be appropriately selected in
accordance with the type of curing agent used in combination, the
application, and the like. In an example of the process, the
curable resin composition of the present invention is heated in the
temperature range of about 20.degree. C. to 250.degree. C. Examples
of the form of the cured product include a laminate, a cast
product, an adhesive layer, a coating film, and a film.
Examples of the applications of the curable resin composition of
the present invention include printed wiring board materials,
resist ink, electrically conductive pastes, interlayer insulation
materials for build-up substrates, adhesive films for build-up,
casting resin materials, and adhesives.
Among these various applications, in the applications of a printed
wiring board and an adhesive film for build-up, the curable resin
composition of the present invention can be used as an insulating
material for a so-called electronic component built-in substrate in
which a passive component such as a capacitor and an active
component such as an integrated circuit (IC) chip are buried in a
substrate. Among these, from the standpoint of characteristics such
as high heat resistance, low thermal expansion, and solubility in
solvents, the curable resin composition of the present invention is
preferably used in printed wiring board materials, resist ink,
electrically conductive pastes, interlayer insulation materials for
build-up substrates, and adhesive films for build-up. In
particular, in the present invention, the solubility of the epoxy
resin itself in solvents is markedly improved, and furthermore,
heat resistance and low thermal expansion are exhibited in cured
products of the resin, and thus the curable resin composition is
most preferably used for printed wiring board materials.
Here, a printed wiring board of the present invention is obtained
by impregnating a reinforcing base material with the
above-described varnish-like curable resin composition containing
the organic solvent (C), laminating a copper foil, and performing
thermocompression bonding. Examples of the reinforcing base
material that can be used here include paper, a glass cloth, a
glass nonwoven cloth, aramid paper, an aramid cloth, a glass mat,
and a glass roving cloth. The process will be further described in
detail. First, the above-mentioned varnish-like curable resin
composition is heated at a temperature suitable for the type of
solvent used, preferably in the range of 50.degree. C. to
170.degree. C. to prepare a prepreg, which is a cured product.
Although the mass ratio of the resin composition to the reinforcing
base material used in this case is not particularly limited, in
general, the content of the resin in the prepreg is preferably
adjusted to 20% to 60% by mass. Next, prepregs prepared as
described above are laminated by a conventional process, a copper
foil is appropriately laminated thereon, and thermocompression
bonding is performed at 170.degree. C. to 250.degree. C. under the
pressure of 1 to 10 MPa for 10 minutes to 3 hours. Thus, a target
printed wiring board can be obtained.
Next, a process for producing, for example, resist ink among the
above-mentioned various applications will be described. For
example, a cationic polymerization catalyst is used as the curing
agent (B) in the curable resin composition, and a pigment, talc,
and a filler are added to the composition, thus obtaining target
resist ink. As for a process for using this resist ink, the resist
ink obtained as described above is applied onto a printed board by
a screen printing process, and a resist ink cured product is then
formed.
Examples of the process for producing an electrically conductive
paste from the curable resin composition of the present invention
includes process in which electrically conductive fine particles
are dispersed in the curable resin composition to prepare a
composition for an anisotropic electrically conductive film, a
paste resin composition for connection of circuits, the paste resin
composition being a liquid at room temperature, or an anisotropic
electrically conductive adhesive.
The above-mentioned interlayer insulation material for a build-up
substrate can be obtained by appropriately blending a rubber, a
filler, and the like with the curable resin composition described
above. In order to produce a build-up substrate using this
material, first, the curable resin composition is applied onto a
wiring board having circuits thereon by a spray coating process, a
curtain coating process, or the like, and is then cured.
Subsequently, predetermined through-hole portions and the like are
formed if necessary. The resulting wiring board is then treated
with a roughening agent, and the surface thereof is washed with hot
water, thereby forming irregularities. The surface is then plated
with a metal such as copper. The plating process is preferably an
electroless plating or electrolytic plating treatment. Examples of
the roughening agent include an oxidizing agent, an alkali, and an
organic solvent. This operation is sequentially repeated according
to need, and a resin insulating layer and an electrically
conductive layer of a predetermined circuit pattern are formed so
that the layers are alternately built up. Thus, a build-up
substrate can be obtained. However, the formation of the
through-hole portions is performed after the outermost resin
insulating layer is formed. Alternatively, it is also possible to
produce a build-up substrate by compression-bonding a copper foil
coated with a resin obtained semi-curing the resin composition on a
wiring board having circuits thereon under heating at 170.degree.
C. to 250.degree. C. without conducting the steps of forming a
roughened surface and performing a plating treatment.
A process for producing an adhesive film for build-up from the
curable resin composition of the present invention is as follows.
For example, the curable resin composition of the present invention
is applied onto a support film to form a resin composition layer,
and the resulting film is used as an adhesive film for a
multi-layer printed wiring board.
When the curable resin composition of the present invention is used
in an adhesive film for build-up, it is important that the adhesive
film be softened under the temperature condition (usually
70.degree. C. to 140.degree. C.) of the lamination in a vacuum
lamination process, and exhibit fluidity (resin flow) sufficient
for filling a via hole or a through-hole present in a circuit board
with the resin at the same time of the lamination of the circuit
board. It is preferable to blend the above-mentioned components so
that the adhesive film exhibits such properties.
Here, the diameter of a through-hole of a multi-layer printed
wiring board is usually 0.1 to 0.5 mm and the depth thereof is
usually 0.1 to 1.2 mm. Usually, it is preferable that the resin can
be filled within these ranges. Note that when lamination is
performed on both surfaces of a circuit board, it is desirable to
fill about 1/2 of a through-hole.
Specifically, the above-described adhesive film can be produced as
follows. A varnish-like curable resin composition of the present
invention is prepared, and this varnish-like composition is then
applied onto a surface of a support film (Y). Furthermore, an
organic solvent is dried by heating, blowing a hot wind, or the
like to form a layer (X) of the curable resin composition.
The thickness of the layer (X) formed is usually equal to or larger
than the thickness of an electrically conductive layer. Since the
thickness of an electrically conductive layer of a circuit board is
usually in the range of 5 to 70 .mu.m, the layer of the resin
composition preferably has a thickness in the range of 10 to 100
.mu.m.
Note that the layer (X) in the present invention may be protected
with a protective film described below. By protecting with the
protective film, it is possible to prevent adhesion of
contaminations and the like and formation of scratches on the
surface of the layer of the resin composition.
Examples of the above-mentioned support film and the protective
film include polyolefins such as polyethylene, polypropylene, and
polyvinyl chloride; polyesters such as polyethylene terephthalate
(hereinafter may be abbreviated as "PET") and polyethylene
naphthalate; polycarbonates; polyimides; release paper; and metal
foils such as a copper foil and an aluminum foil. Note that the
support film and the protective film may be subjected to a release
treatment besides a mat treatment or a corona treatment.
The thickness of the support film is not particularly limited, but
is usually in the range of 10 to 150 .mu.m, and preferably in the
range of 25 to 50 .mu.m. The thickness of the protective film is
preferably in the range of 1 to 40 .mu.m.
The above-described support film (Y) is detached after the adhesive
film is laminated on a circuit board or after an insulating layer
is formed by heat curing. When the support film (Y) is detached
after the adhesive film is cured by heating, it is possible to
prevent adhesion of contamination and the like in the curing step.
In the case where the support film (Y) is detached after the
curing, a release treatment is usually performed on the support
film in advance.
Next, a process for producing a multi-layer printed wiring board
using the adhesive film obtained as described above will be
described. For example, when the layer (X) is protected with a
protected film, the protective film is detached, and the layer (X)
is then laminated on one surface or each surface of a circuit board
so as to directly contact the circuit board by, for example, a
vacuum lamination process. The process of lamination may be a batch
process or a continuous process using a roll. Before the
lamination, the adhesive film and the circuit board may be heated
(preheated) if necessary.
As for the conditions for the lamination, the compression-bonding
temperature (lamination temperature) is preferably set to
70.degree. C. to 140.degree. C., and pressure during the
compression bonding is preferably set to 1 to 11 kgf/cm.sup.2
(9.8.times.10.sup.4 to 107.9.times.10.sup.4 N/m.sup.2), and the
lamination is preferably performed under reduced pressure,
specifically, an air pressure of 20 mmHg (26.7 hPa) or less.
EXAMPLES
Next, the present invention will be specifically described by way
of Examples and Comparative Examples. In the description below, the
"part" and "%" are based on the mass unless otherwise stated. Note
that the melt viscosity at 150.degree. C., and GPC, NMR, and MS
spectra were measured under the following conditions.
1) Melt viscosity at 150.degree. C.: In accordance with ASTM
D4287
2) Method for measuring softening point: JIS K7234
3) GPC: The measurement conditions were as follows:
Measuring apparatus: "HLC-8220 GPC" produced by Tosoh
Corporation
Columns: Guard column "H.sub.XL-L" produced by Tosoh Corporation
"TSK-GEL G2000HXL" produced by Tosoh Corporation "TSK-GEL G2000HXL"
produced by Tosoh Corporation "TSK-GEL G3000HXL" produced by Tosoh
Corporation "TSK-GEL G4000HXL" produced by Tosoh Corporation
Detector: RI (differential refractometer)
Data processing: "GPC-8020 model II Version 4.10" produced by Tosoh
Corporation
Measurement Conditions:
TABLE-US-00001 Column temperature 40.degree. C. Developing solvent
Tetrahydrofuran Flow rate 1.0 mL/min.
Standard: In accordance with a measurement manual of the "GPC-8020
model II Version 4.10", the following monodisperse polystyrenes
having known molecular weights were used.
(Polystyrenes used)
"A-500" produced by Tosoh Corporation
"A-1000" produced by Tosoh Corporation
"A-2500" produced by Tosoh Corporation
"A-5000" produced by Tosoh Corporation
"F-1" produced by Tosoh Corporation
"F-2" produced by Tosoh Corporation
"F-4" produced by Tosoh Corporation
"F-10" produced by Tosoh Corporation
"F-20" produced by Tosoh Corporation
"F-40" produced by Tosoh Corporation
"F-80" produced by Tosoh Corporation
"F-128" produced by Tosoh Corporation
Sample: Each sample (50 .mu.L) was prepared by filtering a 1.0% by
mass tetrahydrofuran solution in terms of resin solid content with
a microfilter.
4) NMR: NMR GSX270 produced by JEOL Ltd.
5) MS: Double-focusing mass spectrometer .DELTA.X505H (FD505H)
produced by JEOL Ltd.
Example 1
To a flask equipped with a thermometer, a dropping funnel, a
condenser, a distilling tube, and a stirrer, 240 parts (1.50 moles)
of 2,7-dihydroxynaphthalene, 85 parts (1.05 moles) of a 37% by mass
aqueous formaldehyde solution, 376 parts of isopropyl alcohol, and
88 parts (0.75 moles) of a 48% aqueous potassium hydroxide solution
were charged, and the mixture was stirred at room temperature while
blowing nitrogen. Subsequently, the temperature was increased to
75.degree. C., and stirring was conducted for two hours. After the
completion of the reaction, 108 parts of sodium dihydrogen
phosphate was added to neutralize the reaction solution. Isopropyl
alcohol was then removed under reduced pressure, and 480 parts of
methyl isobutyl ketone was added thereto. The resulting organic
layer was repeatedly washed with 200 parts of water three times,
and methyl isobutyl ketone was then removed by heating under
reduced pressure. Thus, 245 parts of a phenolic compound (A-1) was
obtained. The phenolic compound (A-1) had a hydroxyl equivalent of
84 g/eq. FIG. 1 shows a GPC chart of the prepared phenolic
compound, FIG. 2 shows a .sup.13C-NMR chart thereof, and FIG. 3
shows a MS spectrum thereof. Referring to the .sup.13C-NMR chart, a
peak showing the generation of a carbonyl group was detected near
203 ppm. In addition, referring to the MS spectrum, a peak of 344
showing a raw material phenol represented by a structural formula
below:
##STR00016## was detected.
Subsequently, 84 parts (hydroxyl group 1.0 equivalent) of the
phenolic compound (A-1) obtained by the above reaction, 463 parts
(5.0 moles) of epichlorohydrin, and 53 parts of n-butanol were
charged to a flask equipped with a thermometer, a condenser, and a
stirrer while purging nitrogen gas to dissolve the compound. The
temperature was increased to 50.degree. C., and 220 parts (1.10
moles) of a 20% aqueous sodium hydroxide solution was then added to
the resulting solution over a period of three hours. Subsequently,
the solution was further allowed to react at 50.degree. C. for one
hour. After the completion of the reaction, unreacted
epichlorohydrin was distilled off at 150.degree. C. under reduced
pressure. Subsequently, 300 parts of methyl isobutyl ketone and 50
parts of n-butanol were added to the crude epoxy resin thus
obtained to dissolve the crude epoxy resin. Furthermore, 15 parts
of a 10% by mass aqueous sodium hydroxide solution was added to the
solution, and was allowed to react at 80.degree. C. for two hours.
Subsequently, washing with 100 parts of water was repeated three
times until the pH of the washed liquid became neutral. Next, the
inside of the system was dehydrated by azeotrope, and
microfiltration was performed. Subsequently, the solvent was
distilled off under reduced pressure to obtain 126 parts of a
target epoxy resin (A-2). The prepared epoxy resin (A-2) had a
softening point of 95.degree. C. (B&R process), a melt
viscosity of 9.0 dPas (measuring process: ICI viscometer process,
measurement temperature: 150.degree. C.), and an epoxy equivalent
of 170 g/eq. FIG. 4 shows a GPC chart of the prepared epoxy resin,
FIG. 5 shows a .sup.13C-NMR chart thereof, and FIG. 6 shows a MS
spectrum thereof. Referring to the .sup.13C-NMR chart, a peak
showing the generation of a carbonyl group was detected near 203
ppm. In addition, referring to the MS spectrum, a peak of 512
showing structural formula (i-.alpha.) below:
##STR00017## was detected.
In addition, the epoxy resin (A-2) contained 10.5% by mass of the
compound represented by structural formula (i-.alpha.) above, 39.6%
by mass of a compound represented by structural formula (i-.beta.)
below:
##STR00018## and 49.9% by mass of other oligomer components.
Example 2
A target epoxy resin (A-3) (128 parts) was obtained as in Example 1
except that the amount of 37% aqueous formaldehyde solution was
changed to 122 parts (1.50 moles). The prepared epoxy resin (A-3)
had a softening point of 98.degree. C. (B&R process), a melt
viscosity of 18.0 dPas (measuring process: ICI viscometer process,
measurement temperature: 150.degree. C.), and an epoxy equivalent
of 178 g/eq. FIG. 7 shows a GPC chart of the prepared epoxy resin,
FIG. 8 shows a .sup.13C-NMR chart thereof, and FIG. 9 shows a MS
spectrum thereof. Referring to the .sup.13C-NMR chart, a peak
showing the generation of a carbonyl group was detected near 203
ppm. In addition, referring to the MS spectrum, a peak of 512
showing structural formula (i-.alpha.) above was detected.
In addition, the epoxy resin (A-3) contained 15.5% by mass of the
compound represented by structural formula (i-.alpha.) above, 20.7%
by mass of the compound represented by structural formula
(i-.beta.) above, and 63.8% by mass of other oligomer
components.
Examples 3 and 4 and Comparative Example 1
The epoxy resin (A-2), the epoxy resin (A-3), and an epoxy resin
(A-4) for comparison [tetrafunctional naphthalene epoxy resin
represented by structural formula below:
##STR00019## ("EPICLON HP-4700" produced by DIC Corporation, epoxy
equivalent 165 g/eq)], all of which function as epoxy resins, a
phenol novolac-type phenolic resin ("TD-2131" produced by DIC
Corporation, hydroxyl equivalent 104 g/eq) functioning as a curing
agent, and triphenylphosphine (TPP) functioning as a curing
accelerator were used and blended so as to have the compositions
shown in Table 1. Each of the resulting resin compositions was cast
in a mold having dimensions of 11 cm.times.9 cm.times.2.4 mm, and
was molded by pressing at a temperature of 150.degree. C. for 10
minutes. The resulting molded product was then taken out from the
mold, and then post-cured at a temperature of 175.degree. C. for
five hours. Thus, samples were prepared. Heat resistance and the
coefficient of linear expansion were evaluated. Furthermore, the
solubility of the epoxy resin (A-2), the epoxy resin (A-3), and the
epoxy resin (A-4) in a solvent was measured by the process
described below. Table 1 shows the results. <Heat Resistance
(Glass Transition Temperature)>
A temperature at which a change in the modulus of elasticity became
maximum (the rate of change in tan .delta. was the largest) was
evaluated as the glass transition temperature using a
viscoelasticity measuring apparatus (DMA: solid viscoelasticity
measuring apparatus RSA-II produced by Rheometric Scientific Inc.,
rectangular tension mode; frequency 1 Hz, temperature-increasing
rate 3.degree. C./min).
<Coefficient of Linear Expansion>
Thermomechanical analysis was conducted using a thermomechanical
analyzer (TMA: SS-6100 manufactured by Seiko Instruments Inc.) in a
compression mode.
Measurement conditions
Measuring load: 88.8 mN
Temperature-increasing rate: Twice at 3.degree. C./min
Measurement temperature range: -50.degree. C. to 300.degree. C.
The measurement under the above conditions was conducted twice for
the same sample. An average coefficient of expansion in the
temperature range of 25.degree. C. to 280.degree. C. in the second
measurement was evaluated as the coefficient of linear
expansion.
<Solubility in Solvent>
In a sample bottle, 10 parts of an epoxy resin was dissolved in 4.3
parts of methyl ethyl ketone at 60.degree. C. in a sealed state.
Subsequently, the solution was cooled to 25.degree. C. and whether
crystals were precipitated or not was evaluated. When no crystals
were precipitated, the sample was evaluated as "good". When
crystals were precipitated, the sample was evaluated as "poor".
TABLE-US-00002 TABLE 1 Comparative Example 3 Example 4 Example 1
Epoxy resin A-2 62.0 A-3 63.1 A-4 61.3 Curing agent TD-2131 38 36.9
38.7 TPP 1 1 1 Heat resistance (.degree. C.) 253 264 235
Coefficient of linear 83 71 90 expansion (ppm) Solubility in
solvent Good Good Poor
Example 5 and Comparative Example 2
In accordance with the compositions shown in Table 2 below, an
epoxy resin, a phenol novolac-type phenolic resin ("TD-2090"
produced by DIC Corporation, hydroxyl equivalent 105 g/eq)
functioning as a curing agent, and 2-ethyl-4-methylimidazole
(2E4MZ) functioning as a curing accelerator were blended, and
methyl ethyl ketone was blended so that the non-volatile matter
(N.V.) of each composition was finally adjusted to 58% by mass.
Subsequently, each of the compositions was cured under the
conditions below to experimentally produce a laminate, and heat
resistance and the coefficient of thermal expansion were evaluated
by the process described below. Table 2 shows the results.
<Conditions for Preparation of Laminate>
Base material: Glass cloth "#2116" (210.times.280 mm) produced by
Nitto Boseki Co., Ltd.
The number of plys: 6, Conditions for forming prepreg: 160.degree.
C.
Curing condition: 1.5 hours at 200.degree. C. and 40 kg/cm.sup.2,
Sheet thickness after forming: 0.8 mm
<Heat Resistance (Glass Transition Temperature)>
The laminate was cut out to have a size of 5 mm.times.54
mm.times.0.8 mm, and this was used as a test specimen. A
temperature at which a change in the modulus of elasticity became
maximum (the rate of change in tan .delta. was the largest) was
evaluated as the glass transition temperature using a
viscoelasticity measuring apparatus (DMA: solid viscoelasticity
measuring apparatus "RSA-II" produced by Rheometric Scientific
Inc., rectangular tension mode: frequency 1 Hz,
temperature-increasing rate 3.degree. C./min).
<Coefficient of Linear Expansion>
The laminate was cut out to have a size of 5 mm.times.5
mm.times.0.8 mm, and this was used as a test specimen.
Thermomechanical analysis was conducted using a thermomechanical
analyzer (TMA: SS-6100 manufactured by Seiko Instruments Inc.) in a
compression mode.
Measurement conditions Measuring load: 88.8 mN
Temperature-increasing rate: Twice at 3.degree. C./min Measurement
temperature range: -50.degree. C. to 300.degree. C.
The measurement under the above conditions was conducted twice for
the same sample. An average coefficient of expansion in the
temperature range of 240.degree. C. to 280.degree. C. in the second
measurement was evaluated as the coefficient of linear
expansion.
TABLE-US-00003 TABLE 2 Comparative Example 5 Example 2 Epoxy resin
A-2 61.8 A-4 61.1 Curing agent TD-2090 38.2 38.9 2E4MZ 0.05 0.075
Heat resistance (.degree. C.) 266 200 Coefficient of linear 204 283
expansion (ppm)
* * * * *